Evolution of the FOX...

[marshallmosty]

Since I dislocated my shoulder, I knew I had some time between Hallett and ECR... Something Richard Pedersen said at Hallett really struck me.

 

"Why try and move everything to the back for weight balance when you can just move the entire car..."

 

Well, that's what I've done.. The rear axle is now 1" further forward and the front hubs are 2 1/2" further forward since the last time anyone has seen the car.

 

Rear End

I started by cutting out the rear torque boxes (they suck anyway, right) and building my own boxes from 1/4" and 1/8" plate. This would allow me to go from a 14" tubular rear control arm to a 23" tubular rear control arm, ala "World Challenge" of the early 90's... The torque arm frame mount was welded in, so I had to shorten the torque arm by an inch. Since the rear end was 1" further forward, I wanted to keep the relative angle of the rear shocks the same, so we built some aluminum spacers 1" thick in the same contour as the shock mount. I had to have a custom driveshaft built which is 1.5" shorter than stock to ensure I don't destroy the tranny under bump. I can't leave well enough alone, and to allow for more tuning, I cut out the panhard bar and installed a Griggs Racing Watts Link so I can adjust the rear roll center. With the rear moved forward 1", the tire still can go thru full compression without hitting the wheel well. I still have to flare to use the 1" spacers. For ECR, it will most likely run a narrow track width, unless I get really good at building flares between then and now...

 

 

Marshall's take on World Challenge torque boxes

 

Here they are installed.

 

Torque arm in pieces

 

Torque arm back together

 

Rear partially assembled with rear shock spacers installed.

 

Watts link partially installed (no frame mount yet)

 

Rear moved forward 1".

 

What I will eventually cover with some DTM style box flares, which hopefully will be integrated into side skirts... maybe.

 

 

Front End

To move the front track forward, my idea was to utilize the stock MM K-member and modify the lower arms to accept heim joints and them push the arms further forward. Nothing that a few weld inserts and rod ends from Coleman can't handle. The front went forward about 2 1/2", so I had to move the rack as well. I was able to get right at an inch of foward movement before the front oil pan sump stopped me. There is no real way to move the rack in front of the oil pan (at least that I could tell). I still have to finish cutting the fenders and dealing with how to flare/cover what I have left.

 

Control arms in pieces

 

Here is a picture of the front assembled, but without the spacers between the rod ends and the heim joints... Those were custom made to measure.

 

Silver spacers on the rack and pinion.

 

Here is what I ended up with... 102.25" wheelbase

 

Flares anyone??

 

 

Front track is 74.25" and wheelbase is 102.5" now... Figured I'd run a bit shot/narrow just incase somebody's tape measure is shorter than mine...

 

And incase someone wants to copy the front flares, they are 280Z rear flares... Pretty easy to work with. Got the idea from Ed Hunter (AI guy).

 

 

 

 

 

Do we ever get done jacking with any of our crap??? Now I just need to build a compliant dash ....

[pbkelley]

What about the top of the shock towers? Caster Camber plates moved that much?

[T&A Racing]

I would love to know how big of a difference on the scale this makes. Is it back together enough to get it on the scales and compare each corner before and after?

 

Thanks

Mark

[Cobra4B]

That's cool... good idea too

[obzezzed350]

Loving the Enkeis!

[edhunter]

Great work, looking forward to the "tale of the scales". I considered doing the same with my car, but didn't know how to change the front end issues. Built a SLA instead. I love these old foxes... BTW I used the same flares on the rear of my fox, only made them deeper to cover the tires....

 

 

[rpoz27]

You say you moved the rear 1" forward, and the front 2.5" forward. Did you not already have the forward offset K-member and control arms? so in essence, you shifted weight rearward only 1" over what most of us are currently running?

[marshallmosty]

You say you moved the rear 1" forward, and the front 2.5" forward. Did you not already have the forward offset K-member and control arms? so in essence, you shifted weight rearward only 1" over what most of us are currently running?

 

Matt,

I already had the offset MM control arms. The wheelbase stretched by 1.5" with the rear wheels coming forward 1" and the front wheels 2.5".

[marshallmosty]

I would love to know how big of a difference on the scale this makes. Is it back together enough to get it on the scales and compare each corner before and after?

 

Thanks

Mark

 

 

Mark,

I had transmission issues this weekend, so didn't have a chance to properly scale the car. Also, one of the scales were reading really light, so it probably would have messed up the exercise anyway. I should get good numbers in about 4 weeks at the next event (NOLA) if the NASA scales are repaired by then.

 

From a driver's prospective. At ECR last year with a new stroker motor (331 making 323/339) I was able to turn a 2:02.5. This year, after blowing the 331, I went back to my 7 season old 302 (making 298/310) and was running 65lbs heavy due to the tired engine. Even with that handicap, I was able to crack off a 2:01.1... The car feel didn't really change much, which was a nice suprise. Everything was very balanced. I do think I have a bit too much ackerman, so I'll probably move the wheel back 0.25", as the inside tire was scrubbing during turns (could hear it howl).

 

Also, some had worried about the excessive caster (yet to be measured) and it's effect on the steering effort. I use a very small wheel and didn't have any issues except low RPM when the pump wasn't providing much assistance (paddock, pit, etc), but there were no issues on track with steering effort.

 

Otherwise, worth the money and effort.

[marshallmosty]

Finally got the car ballasted (220#) and corner weighted.

 

Before Franken-FOX suspension

F/R: 54/46

 

After Franken-FOX suspension

F/R: 57/43

 

Car is now at 3150 with a 50.8% cross weight, as most our tracks in TX are run CCW.

[Cobra4B]

How in the world did it get more nose-heavy?

[kbrew8991]

I'm guessing typo 54/46 as after...

[marshallmosty]

That's what I get for typing on my BB...

 

Finally got the car ballasted (220#) and corner weighted.

 

Before Franken-FOX suspension

F/R: 57/43

 

After Franken-FOX suspension

F/R: 54/46

 

Car is now at 3150 with a 50.8% cross weight, as most our tracks in TX are run CCW.

[Grizlbits]

So Marshall, you did all that work and you moved 95# from the front to the rear.... There must be an easier way. Could you have gotten a similar result or better by making a rear bumper with 200 pounds on the bottom right side of the bumper? I think I could make a chubby bumper with 200 pounds (your ballast) in a couple hours (I have MaD Skilz yo!) and made 53/47!

[marshallmosty]

So Marshall, you did all that work and you moved 95# from the front to the rear.... There must be an easier way. Could you have gotten a similar result or better by making a rear bumper with 200 pounds on the bottom right side of the bumper? I think I could make a chubby bumper with 200 pounds (your ballast) in a couple hours (I have MaD Skilz yo!) and made 53/47!

 

Chris,

I'm an Engineer, so like the challenge... I could take more ballast and put it in the bumper, but the polar moment of inertia would get out of whack and the tail would be wagging the dog, so to speak. I have 160 lbs under the car (80 per side) above the mufflers, under where the back seats used to be. All my ballast is between the axle centerlines.

 

I have a C-channel aluminum rear bumper, so could easily take it off and pour in some lead for extra ballast and bolt thru a backing plate... Might try that at some point and take the 40# out of my passenger floorboard...

[Grizlbits]

If you have understeer, it will help you turn if it is rearward of the rear axle centerline.

Left-Right-Left or other transitions may suck; but tankslappers are great for the spectators to watch!

[marshallmosty]

If you have understeer, it will help you turn if it is rearward of the rear axle centerline.

Left-Right-Left or other transitions may suck; but tankslappers are great for the spectators to watch!

 

True... Like a Porsche 911/996... I've ordered 50lbs of lead to "play" with.. Still need to build a diffuser, so that will put more weight on the rear as well.

[99cobra2881]

Make a mold and cast the diffuser out of lead.

[marshallmosty]

Make a mold and cast the diffuser out of lead.

 

That would definately be "out back and down low"... I'm thinking of stuffing the bumper because that's the easiest to do.

[nape]

No way, PMOI over weight distribution.

 

I dropped 55lbs from the rear axle centerline to the rear bumper last season and it was a huge help on smaller tracks/tighter corners.

[edhunter]

Make a mold and cast the diffuser out of lead.

 

That would definately be "out back and down low"... I'm thinking of stuffing the bumper because that's the easiest to do.

 

Marshall, on my fox car last year, I ran ~140lbs bolted to the inner right rear frame rail, in the general vicinity of the old torque box. I had done the world challenge longer control arm modification as well, still had plenty of room. Low, in front of the axle, but primarily on the RR corner too. I used 2"x6" rectangular steel tube, filled with melted lead from wheel weights. You don't need much room to hang a significant amount of weight this way...

[marshallmosty]

Make a mold and cast the diffuser out of lead.

 

That would definately be "out back and down low"... I'm thinking of stuffing the bumper because that's the easiest to do.

 

Marshall, on my fox car last year, I ran ~140lbs bolted to the inner right rear frame rail, in the general vicinity of the old torque box. I had done the world challenge longer control arm modification as well, still had plenty of room. Low, in front of the axle, but primarily on the RR corner too. I used 2"x6" rectangular steel tube, filled with melted lead from wheel weights. You don't need much room to hang a significant amount of weight this way...

 

Ed,

That's a great idea. Looks like I can take the 40lbs out of the passenger floor and stuff it somewhere like the old torque box. I already have 80# of steel plate on the inside of the frame rail on both sides under the back seat area (160# total).

 

I just hit the dyno today and need 3087. 325/343 was all we could get out of my 331... Guess it will have to do.

[kbrew8991]

please be careful when melting lead - respirator, ventilation, etc - you don't want to be anywhere near those fumes

[wstukas]

No way, PMOI over weight distribution.

 

I dropped 55lbs from the rear axle centerline to the rear bumper last season and it was a huge help on smaller tracks/tighter corners.

 

I'm with TJ on this one. I've moved lead all over my car looking for the "sweet spot" on the scales. It was always faster with the lead in the center of the car, no matter what the scales said.

 

Then came the non-abs rule and I took all the lead out.

 

I'm in the process of doing a similar build on my car, moving the rear axle 1" forward, and the front 3" forward. Should put me 1/2" shy of the max wheelbase. I'm hoping to gain the same 3% swing as you did, that will put me at or near 51% front bias.

[marshallmosty]

No way, PMOI over weight distribution.

 

I dropped 55lbs from the rear axle centerline to the rear bumper last season and it was a huge help on smaller tracks/tighter corners.

 

I'm with TJ on this one. I've moved lead all over my car looking for the "sweet spot" on the scales. It was always faster with the lead in the center of the car, no matter what the scales said.

 

Then came the non-abs rule and I took all the lead out.

 

I'm in the process of doing a similar build on my car, moving the rear axle 1" forward, and the front 3" forward. Should put me 1/2" shy of the max wheelbase. I'm hoping to gain the same 3% swing as you did, that will put me at or near 51% front bias.

 

Will,

That sounds awesome!! the only thing that might further mess my PMOI is taking the 40lbs of steel out of the passenger floorboard and replace that with a similar weight diffuser.

 

Make sure you post pics of your conversion as well.